1. Field of the Invention
The present invention relates to a magnetic head and a magnetic head manufacturing method.
2. Description of Related Art
In recent years advances have been made in making thin-film magnetic heads used in magnetic disk units with greater area recording density and high speed data transfer. Along with making the shape of these thin-film magnetic heads ever more compact, accuracy has also been improved. A thin-film magnetic head with a short magnetic path is particularly effective in device high-speed data transfer. Forming this short magnetic path requires forming a high density coil in limited section of the magnetic head.
To form a coil, usually a plated underlayer is first formed on an alumina and inorganic material containing alumina. A spiral-shaped coil pattern layer of photoresist is then formed, Cu plating is then formed on this and the resist stripped away to form the coil. The so-called pattern plating method is utilized to form the coil conductor. The plated underlayer is then stripped away and resist formed over the entire coil surface to provide insulation between the coil conductor and upper magnetic layer, and coils. The resist in this way is shaped to cover the coil conductor.
[Patent Document 1]
JP-A No. 113812-1988
[Patent Document 2]
JP-A No. 270443-1998
The gap (separation) between the thin-film magnetic head and the magnetic record medium has become lower in recent years leading to a major problem called the thermal protection phenomenon (hereafter: TPR problem). In this phenomenon, when an electric current flows in the coil of the magnetic head, the element protrudes outward due to the rise in temperature in the head and makes unwanted contact with the medium. This TPR problem is caused by poor heat dissipation in the element due to the low heat propagation rate of the resist covering the coil. Resolving this TPR problem requires a better heat propagation rate in the material covering the coil, and improving the heat dissipation of the element.
Achieving a short magnetic path for high speed data transfer requires forming a coil in a limited region (within the head). The limited space requires forming the coil with a narrow pitch. If the resist frame height is made small, then the resist frame width can be made smaller to achieve a narrow pitch frame.
However, the resistance value of the coil conductor currently requires a coil film thickness of at least 1.5 μm so that the minimum required resist film thickness is at least 2.0 μm including the plating film thickness distribution. Reducing the resist frame height with the currently used forming method is therefore impossible. Also, at a narrow coil pitch of 2.0 μm or less, the resist constituting the insulation material (dielectric) cannot fill the area at this pitch and voids 23 occur (FIG. 4).
A technique was disclosed in JP-A No. 113812-1988 (Patent Document 1) for resolving this problem by dry etching an insulating film (dielectric) to form a coil pattern trench and copper plating then performed and the coil conductor formed to specified dimensions by mechanical polishing. However, when the method in JP patent No. 2588392 or JP-A No. 113812-1988 (Patent Document 1) and were actually implemented, the problem occurred that a coil trench with a uniform thickness could not be due to a microloading effect caused by the presence of patterns with different surface areas.
A technique was disclosed in JP-A No. 270443-1998 (Patent Document 2) through semiconductor technology, utilizing an etching stopper layer to counteract the microloading effect.
A pattern plating method forms a resist pattern as an insulating film (dielectric) to cover the coil. However, this method requires heat processing to harden the resist and has the problem that the heat processing causes deterioration of the reproducing element properties.